1. Field of Invention
This invention relates to a cationic ion exchanger whose ion exchange capacity is provided by sulphate groups and to a method for preparation thereof.
2. Description of the Prior Art
Ion exchangers have been known to serve a practical utility in separating components out of fluid mixtures. Exchangers have been developed to allow the chromatographic separation of high molecular weight polyelectrolytes such as proteins (Journal of the American Chemical Society. Vol. 78, 1966, pp 751-755) and to selectively withhold one component from a mixture of macromolecules, such as albumin on QAE-Sephadex from all other serum proteins. Such ion exchangers commonly have attached to them carboxylic or sulphonic acid groups or salts thereof, an amino group or a quaternary amino group.
Ion exchangers operate on charge-charge relationships and, are not normally expected to be particularly selective in separating species of similar charge within a fluid mixture.
It is known that sulphate groups have a strong interaction with proteins. We have now found unexpectedly that sulphated cationic ion exchangers have a selective affinity for lipoproteins in blood serum.
Fractional separation of the various species of proteins in blood plasma or serum is of considerable medical and commercial importance. Methods of isolation of any one of the plasma or serum proteins, however, is hindered by a variety of technical problems, a major one being the presence of sizable amounts of lipoproteins. These are not easily removed selectively, particularly on a large scale.
Thus an ion exchanger which selectively removes lipoproteins and which has a high flow capacity would be a highly desirable product and promote economies in processes for recovering protein species from plasma or serum.
In addition, the quantisation of lipoproteins in human blood is of considerable medical interest. Elevated plasma lipoprotein concentration is frequently a secondary phenomenon associated with primary diseases such as diabetes mellitus, hypothyroidism, heavy proteinuria and obstructive jaundice. In addition, data suggest a direct correlation between plasma lipoprotein concentration and the incidence of clinical coronary artery disease. An ion exchanger which allows for a simple method of testing for elevated lipoprotein concentration is thus highly desirable.
We have found that we can prepare a sulphated ion exchanger using known ion exchange matrices and known sulphating agents. The extent of the sulphation of such an ion exchanger is satisfactory for the acceptable recovery of lipoproteins. We have found that the degree of sulphation can be enhanced without concurrent loss in flow rate capacity by the addition of hydroxy lower alkyl group to the matrix prior to the step of sulphation.
It is an object of this invention to provide a sulphated ion exchanger with a capacity for selectively absorbing lipoproteins or at least to provide the public with a useful choice.